1. Technical Field
The present invention relates to a hand tool and more particularly, to a hand tool capable of driving more than one fastener simultaneously and tightening the fasteners to equal a calculated torque.
2. Description of the Related Art
In the process of assembling two or more workpieces together or locating workpieces on a worktable, a number of fasteners such as cap screws or studs are usually adopted to connect or fasten those workpieces. Referring to FIG. 4, a first workpiece 310 and a second workpiece 320 are joined by a bolted joint 330, and two spring pads 340 are respectively disposed between the first and second workpieces 310 and 320. Each bolted joint 330 includes a cap screw 332 that captures and joins the fist workpiece 310, the spring pad 340 and the second workpiece 320, and a nut 334 for securing the cap screw 332. The cap screws 332 are symmetrically located on the first and second workpieces 310, 320. When a cap screw 310 is tightened, the spring pad 340 between the first and second workpiece 310, 320 is compressed, while a preload or a torque applied on each cap screw 310 should be controlled accurately to control compressed length of the spring pad 340 in a receivable range so that the first workpiece 310 and the second workpiece 320 can be parallel with each other and be fixed stably evenly, and accurately. However, it is difficult to control the preload or torque applied on each cap screw to get equal compression on the each spring pad because the cap screws installed one by one by possibly more than one operator. Therefore, the second workpiece may not be properly aligned with the first workpiece.
Therefore, it is desired to design a hand tool capable of driving more than one fastener simultaneously and tightening the fasteners to equal a calculated torque.